Image warping, often referred to as ``rubber sheeting,'' represents
the deformation of a domain image space into a range image space. In
this paper, a technique which extends the definition of a rubber-sheet
transformation to allow a polygonal region to be warped into one or
more subsets of itself, where the subsets may be multiply connected,
is described. To do this, it constructs a set of ``slits'' in the
domain image, which correspond to discontinuities and concavities in
the range image, using a technique based on generalized Voronoi
diagrams. The concept of medial axis is extended to describe inner and
outer medial contours of a polygon. Polygonal regions are decomposed
into annular subregions, and path homotopies are introduced to
describe the annular subregions. These constructions motivate the
definition of a ladder, which guides the construction of grid point
pairs necessary to effect the warp itself.